1. Field of the Invention
This invention relates to an improved variable bore ram packer for a ram-type blowout preventer used in oil and gas drilling operations. The improved ram packer can seal on the tapered shoulder of a tool joint of a section of drill pipe as well as a range of straight pipe diameters. Ram-type blowout preventers are part of a pressure control system used in oil and gas drilling operations to control unexpected well bore pressure spikes or xe2x80x9ckicksxe2x80x9d as they are commonly referred to in the industry.
The blowout preventer has a body with a vertical bore and a pair of laterally disposed opposing bonnet assemblies. Each bonnet assembly includes a piston which is laterally moveable within the bonnet assembly by pressurized hydraulic fluid. Replaceable sealing elements called xe2x80x9cpackersxe2x80x9d are mounted within rams attached to the ends of the pistons which extend into the blowout preventer bore. When these pistons are moved to a closed position, commonly referred to as xe2x80x9cclosing the blowout preventerxe2x80x9d or xe2x80x9cclosing the ramsxe2x80x9d, the vertical bore of the blowout preventer is sealed and the xe2x80x9ckickxe2x80x9d is contained. These xe2x80x9cpackersxe2x80x9d are available in a variety of configurations designed to seal the blowout preventer bore when the opposing rams and pistons are moved to their closed position.
One type of ram with packer has ends designed to seal around pipe of a specific size in the blowout preventer bore when the blowout preventer is xe2x80x9cclosed.xe2x80x9d Other rams with packers are configured to seal around a range of pipe sizes. It is the type designed to seal around a range of pipe sizes, called variable bore ram packers to which the present invention is directed. The ram packers form a pressure tight seal during a kick until the well bore pressure can be controlled. The well bore pressure can reach several thousand pounds per square inch during a xe2x80x9ckick.xe2x80x9d Each ram packer has a semicircular opening in its front face to form a seal around 180xc2x0 of the outer periphery of the pipe. When the rams are closed as described above, the opposing ram packers meet and seal the entire 360xc2x0 periphery of the pipe. The novel variable bore ram packer of the present invention also has the ability to seal on the tapered tool joint of a section of drill pipe. This is especially important because when a kick occurs the tapered diameter tool joint may be in the bore of the blowout preventer rather than the straight section of drill pipe. Current designs are not able to effectively seal against such a tapered diameter.
Additionally, the variable bore ram packer is required to seal against the drill pipe during a xe2x80x9cstrippingxe2x80x9d operation. During a stripping operation, the drill pipe is pulled from the well bore with the blowout preventer closed against the drill pipe. This results in enormous wear and tear on the ram packer, particularly the elastomeric sealing element. In an effort to minimize the tearing and loss of mass of the elastomeric sealing element, numerous modifications and additions to the ram packer and particularly the elastomeric sealing element in ram-type blowout preventers have been used. Problems associated with these modifications and additions to the variable bore ram packers include excessive loss of mass of the elastomeric seal element, expensive to manufacture and maintain and requiring special oversized blowout preventer rams to accept the variable bore ram packers. The variable bore ram packer of the current invention offers a substantial improvement by offering a variable bore ram packer which accommodates a range of pipe sizes, that can seal on a tapered tapered section of pipe, i.e., a tool joint, and reduces the forces needed to operate the variable bore packer.
2. Description of Related Art
The use of metal inserts in a conical-type blowout preventer is disclosed in U.S. Pat. No. 2,846,178 to B. S. Minor.
U.S. Pat. No. 3,897,038 to R. K. Le Rouax shows a ram type blowout preventer using metal inserts as an anti-extrusion means.
The use of metal inserts in an annular blowout preventer to control the stress level in the elastomeric packer unit is shown in U.S. Pat. No. 3,917,293 to G. E. Lewis et al.
U.S. Pat. No. 4,099,699 to H. Allen shows the use of irising metal inserts in an annular blowout preventer.
Another example of metal inserts in a variable bore blowout preventer in disclosed in U.S. Pat. No. 4,229,012 to B. C. Williams, III.
U.S. Pat. No. 4,444,404 to G. C. Parks, Jr. shows an example of a variable bore ram packer with interlocking anti-extrusion metal inserts.
Another example of a variable bore ram packer with interlocking anti-extrusion metal inserts is disclosed in U.S. Pat. No. 4,458,876 to G. R. Schaeper et al.
U.S. Pat. No. 4,550,895 to D. U. Shaffer shows an early version of a variable bore ram packer. This apparatus utilizes a plurality of annular segments embedded in the elastomeric rubber to aid in effectuating a seal.
The variable bore ram packer of the present invention is designed for use in a standard ram-type blowout preventer used in oil and gas drilling operations. The blowout preventer has a body with an axial bore, a pair of opposing bonnet assemblies and a pair of opposing rams laterally moveable within the bonnet assemblies by a pressurized fluid source to control flow of well fluids through the blowout preventer body axial bore. The variable bore ram packer includes a ram body, a top seal and a packer member. The packer member is molded of an elastomeric material having a central semi-circular .opening sized to fit closely about a tubular member. The packer member includes a plurality of pillar inserts molded within the elastomeric material around the central semi-circular opening. The packer member and the plurality of pillar inserts are molded into a unitary structure allowing the plurality of pillar inserts to move and seat against different diameter tubular members to prevent extrusion of the elastomeric material between the pillar inserts and the tubular member.
The pillar inserts include a top plate, a bottom plate and a spacer pin positioned therebetween. The top and bottom plates are a substantially triangular shape and in the preferred embodiment are free to rotate relative to the spacer pin independently of one another. Each of the top and bottom plates includes a guide lip and a guide shoulder. The guide lips and guide shoulders of adjacent top plates and the guide lips and guide shoulders of adjacent bottom plates coact to provide an irising motion to the top and bottom plates as the top and bottom plates move and seat against different diameter tubular members. The independent movement of the top and bottom plates allows the top and bottom plates to move and seat against different diameters.
A principal object of the present invention is to provide a variable bore ram packer that allows sealing over a wide range of tubular member diameters that minimizes the force required to operate the variable bore ram packer.
Another object of the present invention is to provide a variable bore ram packer that will reliably maintain a seal against different sized tubular members while minimizing damage to the elastomeric sealing element of the packer.
A final object of the present invention is to provide a variable bore ram packer that can seat and seal around a tapered diameter tubular member such as a drill pipe tool joint.
These with other objects and advantages of the present invention are pointed out with specificness in the claims annexed hereto and form a part of this disclosure. A full and complete understanding of the invention may be had by reference to the accompanying drawings and description of the preferred embodiments.